Printing apparatus

ABSTRACT

A printing apparatus includes a transporting roller formed of a metal plate bent into a cylindrical shape. The transporting roller has a first driving member that transmits a rotational driving force to the transporting roller, and a second driving member that transmits the rotational driving force transmitted thereto to a processing unit that performs printing-related processing. The first and second driving members are provided on one end side of a transporting area where recording media are transported.

BACKGROUND

1. Technical Field

The present invention relates to printing apparatuses.

2. Related Art

There are printing apparatuses for recording information on sheet-like recording media. Such printing apparatuses have a transportation unit for transporting the recording media. The transportation unit includes a transporting roller that rotates to transport the recording media.

The transporting roller has a driving member such as a gear for rotating the transporting roller or for driving another device by the rotation of the transporting roller.

In general, a solid rod-like member is used as the transporting roller. However, because a solid material is heavy, the roller deflects under its own weight, degrading the printing precision. JP-A-2006-289496 discloses a technique for forming a metal plate into a cylindrical shape by bending.

However, if the cylindrical shaft disclosed in JP-A-2006-289496 is used as the transporting roller, the following problems occur.

For example, when a rotational driving force from a motor or the like transmitted to the transporting roller is used to drive another device via a driving member, slip due to the torque acting on the transporting roller occurs at the seam created when the metal plate is formed in a cylindrical shape. This degrades the roundness or the like, significantly decreasing the transportation precision, for example, the recording media are transported in a skewed manner. As a result, there has been a problem of degradation in printing precision.

SUMMARY

An advantage of some aspects of the invention is that it provides a printing apparatus that can suppress degradation in transportation precision.

According to an aspect of the invention, a printing apparatus includes a transporting roller formed of a metal plate bent into a cylindrical shape. The transporting roller has a first driving member that transmits a rotational driving force to the transporting roller, and a second driving member that transmits the rotational driving force transmitted thereto to a processing unit that performs printing-related processing. The first and second driving members are provided on one end side of a transporting area where recording media are transported.

In the printing apparatus according to an aspect of the invention, because the first driving member and the second driving member that apply torque to the transporting roller are provided on one end side of the transporting area, the transporting area of the transporting roller is not subjected to a large torque. Accordingly, it is possible to suppress degradation in transportation precision and printing precision due to slip at a seam in the transporting area of the transporting roller.

The processing unit may operate while the recording media are transported.

Thus, according to an aspect of the invention, even when the second driving member performs processing while the recording media are transported, the transporting area of the transporting roller is not subjected to a large torque. Thus, degradation in transportation precision can be suppressed.

A seam of the metal plate of the transporting roller may include an intermediate straight portion that is located in the transporting area and is formed linearly in the axial direction, and a crossing portion that is located on one end side of the transporting area and is formed by fitting a recess and a projection provided at the end surfaces of the metal plate around the axis so as to extend in a direction intersecting the axial direction.

Thus, according to an aspect of the invention, because the length of the seam in the transporting area can be minimized, degradation in transportation precision and printing precision due to the seam can be suppressed. Furthermore, according to an aspect of the invention, the seam includes a crossing portion extending in a direction intersecting the axial direction on one end side of the transporting area, where the first driving member and the second driving member are provided. Thus, it is possible to prevent the seam from slipping in the axial direction. Accordingly, even when a large torque is applied to the transporting roller via the first driving member and the second driving member, deformation of the transporting roller can be suppressed. Thus, degradation in transportation precision of the transporting roller due to deformation can be suppressed.

Furthermore, a third driving member may be provided on the other end side of the transporting area of the transporting roller, the third driving member transmitting a rotational driving force transmitted thereto to a second processing unit for performing printing-related processing, which does not operate while the recording media are transported.

Thus, according to an aspect of the invention, it is possible to transmit the rotational driving force to a second processing unit that is different from the second driving member to perform the printing-related processing. Because the second processing unit does not operate while the recording media are transported, it does not affect the recording-media transportation precision.

Furthermore, in the above-described configuration, the seam of the metal plate constituting the transporting roller may include an intermediate straight portion that is located in the transporting area and is formed linearly in the axial direction, and a second crossing portion that is located on the other end side of the transporting area and is formed by fitting a recess and a projection provided at the end surfaces of the metal plate around the axis so as to extend in a direction intersecting the axial direction.

Thus, according to an aspect of the invention, it is possible to suppress deformation of the transporting roller on the other end side of the transporting area while suppressing degradation in transportation precision and printing precision due to the seam. Thus, degradation in transportation precision of the transporting roller due to deformation can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a side sectional view of a printer of the invention.

FIG. 2A is a plan view schematically showing the configuration of a transporting portion and a sheet-discharging portion, and FIG. 2B is a view from the direction of arrow IIB.

FIG. 3 is a schematic diagram of the configuration of a transporting roller mechanism.

FIG. 4 is an external perspective view of a roller body.

FIG. 5 is a plan view of a metal plate serving as the base material of the roller body.

FIG. 6A is a perspective view of the relevant part of the roller body, and FIG. 6B is a side sectional view of the relevant part.

FIGS. 7A to 7C show the process of pressing the metal plate.

FIGS. 8A to 8C show the process of pressing the metal plate.

FIGS. 9A to 9C show other shapes of a seam.

FIGS. 10A and 10B are a perspective view and a side view of the relevant part of the roller body, respectively.

FIGS. 11A and 11B are a perspective view and a side view of the relevant part of the roller body, respectively.

FIGS. 12A and 12B are a perspective view and a side view of the relevant part of the roller body, respectively.

FIGS. 13A to 13C are plan views of the relevant part of the metal plate, showing unfolded engaging portions.

FIG. 14 is an enlarged view of the seam of the roller body and the vicinity thereof.

FIG. 15A is a plan view showing the transporting roller, FIG. 15B is a sectional view showing the seam, FIG. 15C is a sectional view showing an opening, and FIG. 15D is a diagram showing a modification of the opening.

FIG. 16 is a schematic diagram showing an example of the configuration of the transporting roller.

FIG. 17 is a schematic diagram showing an example of the configuration of the transporting roller.

FIG. 18 is a sectional view of the metal plate after end surfaces thereof are adjusted.

FIGS. 19A and 19B show a punching process according to an embodiment.

FIGS. 20A to 20C are plan views of the relevant part of the metal plate, showing unfolded engaging portions.

FIGS. 21A and 21C show the seam, and FIG. 21B is a plan view of the metal plate.

FIG. 22 is a perspective view showing the relationship between the transporting roller and a sheet during sheet feeding.

FIGS. 23A to 23C show the shapes of the seam.

FIG. 24A shows the shape of the seam, and 24B shows the operation thereof.

FIG. 25 shows the shape of the seam.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring to FIGS. 1 to 25, a printing apparatus according to an embodiment of the invention will be described below.

Note that the following embodiment shows merely an aspect of the invention and does not limit the invention. It may be modified appropriately within the technical scope of the invention. In the attached drawings, the scale, number, etc., of the structures are different from those of the actual structures for clarity's sake.

First, the configuration of a printer (printing apparatus) 1 according to this embodiment will be described with reference to FIG. 1.

FIG. 1 is a diagram of the overall configuration of the printer 1 according to this embodiment.

The printer 1 is a printing apparatus that ejects ink onto paper, serving as a recording medium, to record information such as characters and images. The printer 1 includes a sheet-feed portion 2, a transporting portion (transportation unit) 3, a sheet-discharging portion 4, a head portion 5, and a control unit CONT.

The sheet-feed portion 2 holds a plurality of recording sheets (sheet materials) P, serving as recording media, and feeds the recording sheets P to the transporting portion 3. The sheet-feed portion 2 includes a sheet-feed tray 21 and a sheet-feed roller 22.

The sheet-feed tray 21 holds a plurality of recording sheets P and is provided at a predetermined angle (about 45°) with respect to the horizontal plane. The recording sheets P are sheet-like recording media on which printing with ink can be performed. Examples of the recording sheets P include normal paper, coated paper, sheets for overhead projectors (OHPs), glossy paper, glossy films, etc.

The sheet-feed roller 22 is a roller that rotates to feed the recording sheets P to the transporting portion 3. The sheet-feed roller 22 is provided on the sheet-feed tray 21, at the transporting portion 3 side. A separation pad (not shown) is provided at a position facing the outer peripheral surface of the sheet-feed roller 22, enabling the recording sheets P to be fed one by one to the transporting portion 3 by the cooperation of the separation pad and the sheet-feed roller 22.

The transporting portion 3 transports the recording sheets P fed from the sheet-feed portion 2 to the sheet-discharging portion 4. Printing on the recording sheets P is performed at the transporting portion 3. The transporting portion 3 includes a transporting roller (cylindrical shaft) 31, driven rollers 32, a platen 33, diamond ribs 34, and a driving unit 6 (see FIG. 2).

The transporting roller 31 rotates to precisely transport the recording sheets P to a predetermined printing position. The transporting roller 31 is a cylindrical shaft that is formed in a substantially cylindrical shape and extends in the horizontal plane and in the direction perpendicular to the transporting direction of the recording sheets P. The transporting roller 31 is supported in a rotatable manner by a pair of substantially U-shaped bearings (not shown) provided on the transporting portion 3 and is rotated by being driven by the driving unit 6. Details of the transporting roller 31 will be described below.

The driven rollers 32 are substantially cylindrical members that are arranged at intervals in the axial direction of the transporting roller 31. As will be described below, the driven rollers 32 are provided in a rotatable manner at a position facing a high-friction layer (described below) of the transporting roller 31 (see FIG. 3). The driven rollers 32 have urging springs (not shown). The driven rollers 32 are urged against the high-friction layer 50 of the transporting roller 31 by the urging force exerted by the urging springs. Thus, the driven rollers 32 are rotated by the rotation of the transporting roller 31. The outer peripheral surfaces of the driven rollers 32 are provided with wear-resistant treatment, e.g., fluorocarbon resin coating, so that wear and damage caused by sliding contact with the high-friction layer 50 are reduced.

The platen 33 supports the recording sheet P from below when the head portion 5 performs printing on the recording sheet P and has a top surface substantially parallel to the horizontal plane.

The diamond ribs 34 are projections that protrude upward from the top surface of the platen 33 and are arranged at intervals in the axial direction of the transporting roller 31. Furthermore, the top surfaces of the diamond ribs 34 are substantially parallel to the horizontal plane and support the recording sheet P from below during printing.

The sheet-discharging portion 4 includes a sheet-discharging roller 41 and a sheet-discharge serrated roller 42 and discharges the recording sheet P after printing from the transporting portion 3. The sheet-discharging roller 41 and the sheet-discharge serrated roller 42 can rotate in opposite directions, thereby drawing and discharging the recording sheet P.

The head portion 5 includes an ejection head 51 and a carriage 52 and ejects ink onto the recording sheet P placed on the transporting portion 3.

The ejection head 51 ejects ink according to the instruction of the control unit CONT, and ejection ports (not shown) of the ejection head 51 are provided to face the top surfaces of the diamond ribs 34. The carriage 52 has the ejection head 51 at the bottom thereof and can reciprocate in the axial direction of the transporting roller 31. Furthermore, the carriage 52 is connected to a driving unit (not shown) that reciprocates the carriage 52 according to the instruction of the control unit CONT.

Next, the configuration for rotationally driving the transporting roller 31 will be described with reference to FIG. 2.

FIG. 2A is a plan view schematically showing the configuration of the transporting portion 3 and the sheet-discharging portion 4, and FIG. 2B is a view from the direction of arrow IIB.

As described above, the transporting portion 3 includes the driving unit 6. The driving unit 6 rotationally drives the transporting roller 31 and includes a motor 61 and a pinion gear 62.

The motor 61 is a motor that rotates the transporting roller 31 according to the instruction of the control unit CONT. That is, the control unit CONT controls and drives the motor 61 to achieve rotation of the transporting roller 31 and accurate transportation of the recording sheet P. The pinion gear 62 is connected to the output shaft of the motor 61.

The transporting roller 31A has a first driving gear (first driving member) 35 and a second driving gear (second driving member) 36 that are provided on one end side (the left side in FIG. 2A), in the lengthwise direction (axial direction), of a transporting area CA (see FIG. 3) that comes into contact with the recording sheet P to transport the recording sheet P, and a third driving gear (third driving member) 37 that is provided on the other end side (the right side in FIG. 2A) of the transporting area CA.

The first driving gear 35 is a gear that rotates the transporting roller 31. The first driving gear 35 is connected to an end of the transporting roller 31 on the driving unit 6 side by press fitting. The first driving gear 35 and the pinion gear 62 are meshed with each other, whereby the driving force of the motor 61 is transmitted to the transporting roller 31 via the pinion gear 62 and the first driving gear 35, rotating the transporting roller 31.

The second driving gear 36 is a gear that transmits the driving force of the motor 61 to the sheet-discharging roller 41 serving as a processing unit. The second driving gear 36 has a smaller diameter than the first driving gear 35 and is disposed adjacent to and coaxially with the first driving gear 35.

The third driving gear 37 transmits the rotational driving force of the transporting roller 31 to another device (a second processing unit) 38, e.g., a pump that covers the nozzles in the ejection head 51 (capping) to perform suction. More specifically, the rotational driving force is transmitted via the third driving gear 37 to a device that does not operate while the transporting roller 31 transports the recording sheet P.

A method for connecting the second driving gear 36 and the third driving gear 37 to the transporting roller 31 will be described below.

The sheet-discharging roller 41 has a sheet-discharge driving gear 43 provided at an end on the driving unit 6 side. Furthermore, an intermediate gear 44 is provided between the sheet-discharge driving gear 43 and the second driving gear 36. The intermediate gear 44 is meshed with both the second driving gear 36 and the sheet-discharge driving gear 43. That is, the driving force of the motor 61 is transmitted to the sheet-discharging roller 41 via the second driving gear 36, the intermediate gear 44, and the sheet-discharge driving gear 43. Thus, rotation of the sheet-discharging roller 41 causes sheet-discharge processing, which is printing-related processing, to be performed.

FIG. 3 is a schematic diagram of the configuration of a transporting roller mechanism 19 formed of the transporting roller 31 and the driven rollers 32.

The transporting roller 31 includes a roller body 16 formed of a metal plate, such as a galvanized steel sheet or a stainless steel sheet, that is formed into a cylindrical shape by pressing, and the high-friction layer 50 provided on the surface of the roller body 16. The high-friction layer 50 has the same length as the transporting area CA corresponding to the recording sheet P having the maximum width that can be printed by the printer 1 and has a resin layer formed of, for example, epoxy resin or polyester resin, and ceramic particles dispersed on the surface of the resin layer. Examples of the ceramic particles include aluminum oxide (alumina), silicon carbide, and silicon dioxide. The particle diameter of the ceramic particles is adjusted by trituration. By using trituration, the ceramic particles have relatively sharp ends.

Furthermore, the ends of the transporting roller 31 are held by bearings 70 so as to be rotatable. The roller body (cylindrical shaft) 16 is formed in a cylindrical shape by pressing a metal plate and bringing opposed ends (end surfaces) toward or into contact with each other. Therefore, the roller body 16 has a seam formed between the ends. In this embodiment, the configuration of the seam near the transporting area CA differs from that at both ends.

More specifically, as shown in FIG. 4, a seam 80 according to this embodiment includes an intermediate straight portion 86 formed in the middle portion of the roller body 16 including the transporting area CA and winding portions 85 formed at both ends of the roller body 16. The above-described high-friction layer 50 is formed on the intermediate straight portion 86. The intermediate straight portion 86 is formed by bending a substantially rectangular metal plate 60 in plan view, as shown in FIG. 5, into a cylindrical shape and connecting together ends (end surfaces) 61 a and 61 b, positioned at the middle portion in the lengthwise direction, of the metal plate 60. Furthermore, the winding portions 85 positioned at both ends of the metal plate 60 in the lengthwise direction have rectangular projections 61 c protruding from the end surface 61 a in the widthwise direction (the peripheral direction around a central axis 16 a when formed in a cylindrical shape) and rectangular recesses 61 d recessed from the end surface 61 b in the widthwise direction (the peripheral direction around a central axis 16 a when formed in a cylindrical shape). The rectangular projections 61 c and the rectangular recesses 61 d have the same widths and are arranged along the central axis 16 a at a constant pitch. As shown in FIG. 4, the winding portions 85 including crossing portions 85 a and crossing portions (second crossing portions) 85 b that extend in a direction crossing the central axis 16 a are formed into a zigzag shape from staggered portions 110 that fit together when the metal plate 60 is formed in a cylindrical shape.

Furthermore, as shown in FIG. 6A, an engaging hole 71 for connecting to the second driving gear 36 shown in FIG. 2 is provided on one end side of the roller body 16 (transporting roller 31), at a position distant from the seam 80. More specifically, the engaging hole 71 in the roller body 16 includes through-holes 71 a and 71 a provided at positions facing each other, i.e., in the surfaces having two points that define the diameter of the roller body 16. Thus, the engaging hole (engaging portion) 71 including these through-holes 71 a and 71 a can be formed. As shown in FIG. 6B, by engaging the second driving gear 36 with the engaging hole 71 using a shaft or a pin (not shown), the second driving gear 36 can be fixed to the roller body 16.

Although not shown in FIG. 6A, the roller body 16 (transporting roller 31) has an engaging hole 72 provided on the other end side, at a position distant from the seam 80. As shown in FIG. 6B, by engaging the third driving gear 37 with the engaging hole 72 using a shaft or a pin (not shown), the third driving gear 37 can be fixed to the roller body 16.

The seam 80 is not shown in FIGS. 6A and 6B.

As a detailed description of the transporting roller 31, a method for producing the transporting roller 31 will be described with reference to FIGS. 5, 7, and 8.

In order to form the transporting roller 31, first, a rectangular plate-like or strip-like large metal plate is prepared. For example, a galvanized steel sheet having a thickness of about 1 mm is used as the large metal plate. Then, the large metal plate is cut by pressing to form a long, narrow, substantially rectangular plate-like metal plate 60 having a size corresponding to the size of the roller body 16, i.e., the metal plate 60 serving as the base material of the roller body 16, as shown in FIG. 5.

When the large metal plate is pressed and cut, in order to form the winding portions at the seam between the ends, the rectangular-wave-like staggered portions 110 are formed at both ends in the lengthwise direction of the ends 61 a and 61 b, which are the long sides facing each other. Furthermore, straight portions 111 are formed between the staggered portions 110 formed at both ends of the long sides (ends).

Because the long sides (the ends 61 a and 61 b) are brought toward or into contact with each other by pressing, the projections of the staggered portion 110 of one long side, of course, correspond to the recesses of the staggered portion 110 of the other long side, and the recesses of the staggered portion 110 of one long side correspond to the projections of the staggered portion 110 of the other long side.

Next, as shown in FIGS. 7A to 7C and 8A to 8C, the metal plate 60 is pressed into a cylindrical (pipe-like) shape so that the ends 61 a and 61 b on both sides (on the long-side sides) are brought toward or into contact with each other.

First, the metal plate 60 is pressed with a male mold 101 and a female mold 102, as shown in FIG. 7A, to bend both sides 62 a and 62 b of the metal plate 60 in an arch shape (substantially ¼ arch is desirable). Although 7A to 7C and 8A to 8C show spaces between the metal plate 60, the male mold 101, and the female mold 102 for clarity's sake, there are no such spaces in actuality, and the metal plate 60, the male mold 101, and the female mold 102 are in tight contact with one another at their contact portions.

Next, using the male mold 103 and the female mold 104 shown in FIG. 7B, the middle portion of the metal plate 60 shown in FIG. 7A in the widthwise direction (bending direction) is pressed and bent into an arch shape (substantially ¼ arch is desirable).

Then, as shown in FIG. 7C, a core mold 105 is disposed inside the metal plate 60 shown in FIG. 7B. Using an upper mold 106 and a lower mold 107 shown in FIG. 7C, the end surfaces (ends) 61 a and 61 b of the both sides 62 a and 62 b of the metal plate 60 are brought toward each other, as shown in FIGS. 8A to 8C.

Herein, the outside diameter of the core mold 105 shown in FIGS. 7C and 8A to 8C is the same as the inside diameter of the cylindrical hollow pipe being formed. Furthermore, the radii of a press surface 106 c of the upper mold 106 and a press surface 107 a of the lower mold 107 are the same as the outside radius of the hollow pipe being formed. Furthermore, as shown in FIGS. 8A to 8C, the upper mold 106 includes a pair of left and right mold segments, and these mold segments 106 a and 106 b can be individually raised and lowered.

From the state shown in FIG. 7C, the upper mold segment 106 a on the right side is lowered relative to the lower mold 107 (hereinafter, the movement of the mold is relative movement), as shown in FIG. 8A, to press and bend one side of the metal plate 60 in a substantially semicircular shape. Similarly to the upper mold 106, the lower mold 107 may include a pair of left and right mold segments (see a segment surface 107 b), and the lower mold segment on the same side may be raised in the process shown in FIG. 8A.

Next, as shown in FIG. 8B, the core mold 105 is slightly lowered (to such an extent that the ends 61 a and 61 b can be brought toward each other), and the upper mold segment 106 b on the other side is lowered to press and bend the other side of the metal plate 60 in a substantially semicircular shape.

Then, as shown in FIG. 8C, the core mold 105 and the upper mold segments 106 a and 106 b are lowered, forming a cylindrical hollow pipe (roller body 16). In this state, the left end 61 a and the right end 61 b are in contact with each other. That is, by bringing the ends 61 a and 61 b of the metal plate 60, serving as the base material, into contact with each other, a seam formed between the ends 61 a and 61 b of the cylindrical hollow pipe.

Next, in this embodiment, the outer peripheral surface of the hollow pipe (roller body 16) is ground by known centerless grinding to increase the roundness of the hollow pipe (roller body 16) and to reduce runout.

As a result, the roundness of the hollow pipe becomes higher than that before centerless grinding, reducing runout of the roller body 16. Furthermore, because the distance between the ends 61 a and 61 b of the roller body (cylindrical shaft) 16 is further reduced, the seam 80 with a reduced distance between the ends 61 a and 61 b is formed.

When the staggered portions 110 shown in FIG. 5 fit together, the winding portions 85 having the crossing portions 85 a and 85 b are formed at both ends of the roller body 16, as shown in FIG. 4.

Once the roller body 16 is formed, the high-friction layer 50 is formed on the surface of the roller body 16.

Although either a dry process or a wet process (or combination of these methods) may be used to form the high-friction layer 50, a dry process is preferably employed.

Next, the operation of the printer (printing apparatus) 1 including the transporting roller mechanism 19 will be described with reference to FIGS. 1 and 2.

When the recording sheet P fed by the sheet-feed roller 22 reaches the upstream vicinity of the transporting roller mechanism 19, the motor 61 drives to introduce the recording sheet P between the transporting roller 31 and the driven rollers 32. Then, the rollers 31 and 32 transport the recording sheet P at a constant speed to a position below the ejection head 51 located on the downstream side.

Because the transporting roller 31 has the high-friction layer 50, and because the driven rollers 32 are arranged at a position where they come into contact with the high-friction layer 50, a force with which the transporting roller 31 and the driven rollers 32 nip the recording sheet P increases. Thus, the efficiency of transporting the recording sheet P further increases.

When the printing start end of the recording sheet P reaches a predetermined printing position immediately below the ejection head 51, printing is started.

Thereafter, when the start end of the recording sheet P reaches the sheet-discharging portion 4, i.e., the sheet-discharging roller 41 and the sheet-discharge serrated roller 42, discharge of the recording sheet P nipped therebetween is started.

Herein, the driving force of the motor 61 is transmitted to the transporting roller 31 via the first driving gear 35 and is then transmitted to the sheet-discharging roller 41 via the second driving gear 36, rotating the sheet-discharging roller 41 while the transporting roller 31 transports the recording sheet P. At this time, because both the first driving gear 35 and the second driving gear 36 are disposed on one end side of the transporting area CA of the transporting roller 31, the torque acting on the transporting roller 31 (roller body 16) does not act on the transporting area CA. Therefore, slip does not occur at the seam 80 (intermediate straight portion 86) in the transporting area CA. Accordingly, it is possible to prevent an inconvenience, such as skewed transportation of the recording sheet P, and to suppress degradation in transportation precision and printing precision.

On the other hand, the driving force of the motor 61 transmitted to the transporting roller 31 via the first driving gear 35 is transmitted to another device 38 via the third driving gear 37. In this case, because the third driving gear 37 is disposed on the other end side of the transporting roller 31 opposite the first driving gear 35 across the transporting area CA, the transporting area CA is subject to the torque exerted by the operation of the device 38. However, because the third driving gear 37 is connected to the device 38, which does not operate while the transporting roller 31 transports the recording sheet P, the recording sheet P is not transported during operation of the device 38. Thus, the transportation precision and the printing precision are not degraded. In addition, in this embodiment, because the seam 80 of the transporting roller 31 in the transporting area CA is the intermediate straight portion 86, and the seam 80 has a minimum length, degradation in transportation precision and printing precision due to the seam 80 can be further suppressed.

As has been described above, in this embodiment, because both the first driving gear 35 and the second driving gear 36 are disposed on one end side of the transporting area CA of the transporting roller 31, degradation in transportation precision and printing precision of the recording sheet P can be suppressed. Furthermore, in this embodiment, because the seam 80 constitutes the winding portion 85, formed by fitting the staggered portions 110, on one end side of the transporting roller 31 where the first driving gear 35 and the second driving gear 36 are disposed, and because the seam 80 has the crossing portions 85 a, it is possible to prevent slip in the central axis 16 a direction from occurring at the seam 80. Thus, deformation of the transporting roller 31 (roller body 16) can be suppressed, and degradation in transportation precision of the transporting roller 31 due to deformation can be suppressed.

Furthermore, in this embodiment, the third driving gear 37 provided on the other end side of the transporting roller 31 is connected to the device 38, which does not operate while the transporting roller 31 transports the recording sheet P. Thus, the driving force of the motor 61 can be efficiently utilized without causing degradation in transportation precision, which contributes to reduction in size and cost of the apparatus. In addition, in this embodiment, because the seam 80 has the crossing portions 85 b on the other end side of the transporting roller 31 where the third driving gear 37 is disposed, it is possible to prevent slip in the central axis 16 a direction from occurring at the seam 80. Thus, deformation of the transporting roller 31 (roller body 16) can be suppressed, and degradation in transportation precision of the transporting roller 31 due to deformation can be suppressed.

Although a preferred embodiment of the invention has been described with reference to the attached drawings, the invention is of course not limited to such an example. The shapes, combinations, and the like of the components described above are merely examples, and they may be variously modified on the basis of the design requirement or the like, within a scope not departing from the gist of the invention.

For example, in the above-described embodiment, the first driving gear 35 and the second driving gear 36 are provided on one end side of the transporting roller 31, and the third driving gear 37 is provided on the other end side of the transporting roller 31. However, the configuration is not limited thereto but may be such that only the first driving gear 35 and the second driving gear 36 are provided on one end side of the transporting roller 31.

Furthermore, the above-described embodiment shows an example in which the rotational driving force transmitted via the second driving gear 36 drives the sheet-discharging roller 41. However, the configuration is not limited thereto but may be such that the rotational driving force is transmitted to another processing unit that performs printing-related processing. In this case, the other processing unit may perform predetermined processing while the recording sheet P is transported by the transporting roller 31 or while the recording sheet P is not transported.

Furthermore, in the above-described embodiment, the winding portions 85 of the seam 80 of the roller body 16 are formed of the rectangular projections 61 c and the rectangular recesses 61 d. However, other than this shape, for example, as shown in FIG. 9A, the crossing portions 85 a of the winding portions 85 may be inclined with respect to the peripheral direction (the top-bottom direction in FIG. 9A) so as to cross the axis parallel to the central axis 16 a at an angle α. This configuration enables the ends of the projections 61 c to easily fit to the corresponding recesses 61 d when the end surfaces are brought toward each other by pressing the metal plate. Thus, the roller body 16 can be prevented from being strained or twisted.

Furthermore, the winding portions 85 may have an alternating arch shape (a sine wave shape), as shown in FIG. 9B, or a zigzag shape formed of triangular projections 61 c and recesses 61 d, as shown in FIG. 9C.

Furthermore, in the above-described embodiment, the second driving gear 36 and the third driving gear 37 are engaged with the engaging holes 71 and 72 provided in the roller body 16, respectively, so that the second driving gear 36 and the third driving gear 37 are mounted to the roller body 16 in a non-rotatable manner. However, the configuration is not limited thereto, and, for example, as shown in FIGS. 10A and 10B, an engaging portion 73, which is a D-shaped cutout, may be formed at an end of the roller body 16. The engaging portion 73 is formed at the end of the cylindrical roller body 16 (transporting roller 31). As shown in FIG. 10A, an opening 73 a is formed by removing a rectangular portion in plan view from the cylindrical roller body 16 so that the side surface at the end has a D shape, as shown in FIG. 10B.

Therefore, by engaging a connecting part such as a gear (not shown) with the D-shaped engaging portion 73, the connecting part can be mounted to the roller body 16 in a non-freewheeling manner. Furthermore, the engaging portion 73 has the slot-like opening 73 a communicating with the inner hole of the hollow pipe (roller body 16). Thus, the connecting part can also be mounted to a developing roller 510 in a non-freewheeling manner using the opening 73 a. More specifically, a projection is formed on the connecting part, and the projection is fitted to the opening 73 a to prevent freewheeling.

Furthermore, as shown in FIGS. 11A and 11B, it is also possible to form an engaging portion 74 having a slot 74 a and a D-shaped cutout portion 74 b at the end of the roller body 16. In this engaging portion 74, the D-shaped cutout portion 74 b is formed at the outer end of the roller body 16, and the slot 74 a is formed on the inner side of the D-shaped cutout portion 74 b. As shown in FIG. 11A, the slot 74 a is formed by cutting a portion of the roller body 16 away in the peripheral direction, up to substantially half. The D-shaped cutout portion 74 b is located on the outer side of the slot 74 a and has an opening 74 c extending in the direction perpendicular to the slot 74 a. The D-shaped cutout portion 74 b has a pair of bent pieces 74 d and 74 d on both sides of the opening 74 c. That is, as shown in FIG. 11B, by bending the bent pieces 74 d and 74 d toward the central axis of the roller body 16, the portions corresponding to the bent pieces 74 d and 74 d are recessed from the cylindrical outer peripheral surface of the roller body 16.

Therefore, by engaging a connecting part such as a gear (not shown) with the slot 74 a or the D-shaped cutout portion 74 b, the connecting part can be mounted to the roller body 16 (transporting roller 31) in a non-freewheeling manner. Furthermore, in this engaging portion 74, the connecting part can also be mounted to the roller body 16 in a non-freewheeling manner using the opening 74 c formed between the bent pieces 74 d. More specifically, a projection is formed on the connecting part, and the projection is fitted to the opening 74 c to prevent freewheeling.

Furthermore, as shown in FIGS. 12A and 12B, it is also possible to form an engaging portion 75 having a slot 75 a and an opening 75 b at the end of the roller body 16. In this engaging portion 75, the opening 75 b is formed at the outer end of the roller body 16, and the slot 75 a is formed on the inner side of the opening 75 b. As shown in FIG. 12A, the slot 75 a is formed by cutting a portion of the roller body 16 away in the peripheral direction, up to substantially half. As shown in FIG. 12B, the opening 75 b is located on the outer side of the slot 75 a and is formed by removing a rectangular portion in plan view from the roller body 16 so that the side surface at the end has a D shape.

Therefore, by engaging a connecting part such as a gear (not shown) with the slot 75 a or a D-shaped portion formed by the opening 75 b, the connecting part can be mounted to the roller body 16 in a non-freewheeling manner. Furthermore, also in this engaging portion 75, similarly to the engaging portion 73 shown in FIGS. 10A and 10B, the connecting part can be mounted to the roller body 16 in a non-freewheeling manner using the opening 75 b.

The engaging hole 71 and the engaging portions 73, 74, and 75 can be provided by cutting the roller body 16 obtained by pressing the above-described metal plate 60. For example, the D-shaped engaging portion 73 shown in FIGS. 10A and 10B can be formed by cutting the end to form the opening 73 a.

However, performing additional machining on the roller body 16 means adding another machining step just for forming the engaging portion and decreases the cost and time efficiencies. Thus, it is preferable that unfolded engaging portions, which constitute the engaging portion when being pressed, be formed in the metal plate before the roller body 16 is pressed, and the engaging portion be formed at the same time when the metal plate is pressed into the roller body 16.

More specifically, when a large metal plate is pressed into the long, narrow, rectangular plate-like metal plate 60, as shown in FIG. 5, unfolded engaging portions in the shape of notches, projections, holes, slots, or the like are formed. For example, as shown in FIG. 13A, the through-holes 71 a and 71 a, which are unfolded engaging portions 76 a, are provided at predetermined positions at an end of the metal plate 60. Then, by pressing the metal plate 60, the through-holes 71 a and 71 a are made to face each other, whereby the engaging hole 71 shown in FIGS. 6A and 6B can be formed.

As shown in FIG. 13B, by forming unfolded engaging portions 76 b by cutting the end of the metal plate 60 in a predetermined shape, the engaging portion 74 shown in FIGS. 11A and 11B can be formed by pressing the metal plate 60. That is, the engaging portion 74 can be formed by forming a pair of notches (recesses) 74 e and 74 e and a pair of projections 74 f and 74 f, which are the unfolded engaging portions 76 b. In this example, however, because the projections 74 f and 74 f need to be bent to the inside and pressed into the bent pieces 74 d after the metal plate 60 is pressed, the cost and time efficiencies in the machining process cannot be sufficiently improved.

As shown in FIG. 13C, by forming unfolded engaging portions 76 c by cutting the end of the at the metal plate 60 in a predetermined shape, the engaging portion 75 shown in FIGS. 12A and 12B can be formed by pressing the metal plate 60. That is, the engaging portion 75 can be formed by forming a pair of notches (recesses) 75 c and 75 c and a pair of projections 75 d and 75 d, which are the unfolded engaging portions 76 c. In this example, by bending the projections 75 d and 75 d into an arch shape when the metal plate 60 is pressed, the opening 75 b shown in FIG. 12B can be formed between the projections 75 d and 75 d. Therefore, there is no need to perform additional machining on the roller body 16 formed by pressing, and the cost and time efficiencies in the machining process can be sufficiently improved.

Furthermore, it is preferable that the ceramic particles (for example, alumina particles) constituting the high-friction layer 50 described in the above embodiment have a particle diameter in the range of 15 μm to 90 μm, and that a weighted average particle diameter (average particle diameter), i.e., the center diameter, be adjusted to 45 μm.

That is, as shown in FIG. 14, alumina particles (inorganic particles) having an average particle diameter (center diameter) larger than the distance d1 (30 μm) at the outer peripheral surface of the seam 80 are used. Furthermore, regarding the particle diameter distribution (size range), it is preferable that particles having an average particle diameter smaller than the distance d1 at the outer peripheral surface of the seam 80 and larger than the distance d2 (10 μm) at the inner peripheral surface be contained. Furthermore, it is preferable that the minimum particle diameter of the particle diameter distribution be larger than the minimum distance between the end surfaces 61 a and 61 b at the seam 80, i.e., the distance d2 at the inner peripheral surface.

By forming the high-friction layer 50 in this manner, no groove due to the gap between the end surfaces 61 a and 61 b of the metal plate 60 is formed especially at the seam 80, and the gap between the end surfaces 61 a and 61 b is filled mainly with the alumina particles 95.

That is, because the alumina particles 95 having an average particle diameter larger than the distance d1 at the outer peripheral surface of the seam 80 are used, most of the alumina particles 95 do not enter the seam 80 but are deposited on the outer peripheral surface of the roller body 16 with a resin film 151 therebetween, as shown in FIG. 14. Therefore, even though the seam 80 has the gap between the end surfaces 61 a and 61 b of the metal plate 60, the groove due to the gap is not formed because the alumina particles 95 cover the gap.

Furthermore, the alumina particles 95 having a particle diameter distribution (size range) such that particles 95 a smaller than the distance d1 at the outer peripheral surface of the seam 80 and larger than the distance d2 (10 μm) at the inner peripheral surface side are contained are used. Thus, the particles 95 a enter the gap formed at the seam 80 and stay there, assuredly preventing a groove due to the seam 80 from being formed.

Furthermore, even if a force acts on the roller body 16 (transporting roller 31) in the direction in which the gap is narrowed when the roller body 16 is used, because the alumina particles 95 a in the gap resist this force, deformation of the roller body 16 (transporting roller 31) can be suppressed. Therefore, in the transporting roller mechanism 19 having the transporting roller 15, uneven transportation due to deformation of the transporting roller 15 is prevented.

Furthermore, the alumina particles 95 whose minimum particle diameter in the particle diameter distribution is larger than the minimum distance between the end surfaces 61 a and 61 b of the seam 80, i.e., the distance d2 at the inner peripheral surface, are used. Thus, no alumina particles 95 enter the roller body 16 through the gap formed at the seam 80, when the high-friction layer 50 is formed by arranging the alumina particles 95 over the surface of the roller body 16. This simplifies the subsequent processing such as cleaning the inside of the roller body 16, increasing the production efficiency.

Furthermore, as shown in FIG. 15A, openings 170 may be provided in some portions of the seam 80 of the roller body 16 shown in the above-described embodiment.

As shown in FIG. 15B, the seam 80 formed in the roller body 16 has a groove-like structure in which the end surfaces 61 a and 61 b are in tight contact with each other at the inner periphery and are separated at the outer periphery.

The seam 80 may also have a structure in which the end surfaces 61 a and 61 b are not in contact with each other and are separated with a small gap therebetween. Because the seam 80 is formed over the overall length of the transporting roller 31, if grease applied to the bearings is deposited on the surface of the transporting roller 31, the grease flows along the seam 80 due to capillarity. In particular, the smaller the seam 80 (the maximum distance d1 between the end surfaces 61 a and 61 b) to increase the strength of the transporting roller 31, the greater the capillarity, making the grease easy to flow along the seam 80.

To counter this, as shown in FIG. 15C, the opening 170 is provided at a portion of the seam 80 of the roller body 16. As shown in FIG. 15C, the opening 170 is formed of notches 76 and 77 provided in the end surfaces 61 a and 61 b, respectively, that constitute the seam 80. The maximum distance d2 between the notches 76 and 77 is set to, for example, about 1 mm or more when the end surfaces 61 a and 61 b are in contact with each other, and the notches 76 and 77 serve as the opening 170.

The opening 170 is provided in an area of the seam 80 formed over the overall length of the transporting roller (roller body 16) except for the areas having the high-friction layer 50 and the areas supported by the bearings 26. That is, because the high-friction layer 50 is formed at substantially the middle portion of the transporting roller 31, and because the ends of the transporting roller 31 are supported by the bearings, the transporting roller 31 has at least two openings 170.

The openings 170 are provided to prevent the grease (lubricant oil) applied to the bearings from flowing along the seam 80 (the gap between the end surfaces 61 a and 61 b) up to the high-friction layer 50. That is, flow of the grease due to capillarity is prevented by providing the openings 170 in some portions of the seam 80. More specifically, by providing the openings 170 in the seam 80, at positions between the area having the high-friction layer 50 and the areas supported by the bearings 26, the grease is prevented from reaching the high-friction layer 50. Then, by adjusting the size of the openings 170 (the maximum distance, d2, between the notches 76 and 77), flow of the grease due to capillarity can be assuredly prevented.

It is not limited to the case where the notches 76 and 77 constituting the openings 170 are provided on the end surfaces 61 a and 61 b forming the seam 80. That is, as shown in FIG. 15D, it is possible that a notch 78 is provided only on one of the end surfaces 61 a and 61 b (for example, the end surface 61 a) forming the seam 80, and the notch 78 and the end surface 61 b constitute the openings 170. Furthermore, the shape of the openings 170 is not limited to rectangular, but may be circular, etc.

Furthermore, the seam 80 formed on the roller body 16 may have a shape shown in FIG. 16. That is, in the seam 80, a first end surface 174 and a second end surface 175 are in contact with each other at the outer peripheral surface 16 a of the roller body 16. The gap between the first end surface 174 and the second end surface 175 gradually increases from the radially outer side to the inner side. Furthermore, the shape of the first end surface 174 and second end surface 175 are the same over the overall length of the roller body 16, except for the winding portions.

Furthermore, the first angle α formed between the first end surface 174 and the outer peripheral surface 16 a and the second angle β formed between the second end surface 175 and the outer peripheral surface 16 a are both smaller than 90°.

The first end surface 174 and the second end surface 175 of the seam 80 are in contact with each other at the outer peripheral surface 16 a, and the smoothness of the outer peripheral surface 16 a increases at the seam 80. Accordingly, when the transporting roller 31 rotates, the outer peripheral surface of the transporting roller 31 can be stably in contact with the recording sheet P. Thus, the recording sheet P can be precisely transported.

The shape of the seam 80 may be such that, as shown in FIG. 17, the first angle α formed between the first end surface 174 of the seam 80 and the outer peripheral surface 16 a is smaller than 90°, and the second angle β formed between the second end surface 175 and the outer peripheral surface 16 a is equal to or larger than 90°. That is, the first end surface 174 and the second end surface 175 at the connecting portion 80 may be inclined toward a predetermined direction in the peripheral direction.

The seam 80 is formed by going through the following process. First, the metal plate 60 is formed by punching in progressive pressing. Then, end-surface adjustment treatment is performed on the first end surface 174 and the second end surface 175 of the metal plate 60 to adjust the inclinations of the first end surface 174 and second end surface 175 with respect to the outer peripheral surface 16 a.

As shown in FIG. 18, the inclinations of the first end surface 174 and second end surface 175 with respect to the outer peripheral surface 16 a are adjusted by pressing. By this adjustment, both the first angle α formed between the first end surface 174 and the outer peripheral surface 16 a and the second angle β formed between the second end surface 175 and the outer peripheral surface 16 a become smaller than 90°.

Therefore, when the metal plate 60 is bent into a cylindrical roller body 16, the first end surface 174 and the second end surface 175 are in contact with each other at least at the outer peripheral surface 16 a.

Because the roller body 16 (transporting roller 31) is formed of the metal plate 60 having a residual curl from a steel plate coil, it is preferable that the inner peripheral surface of the coil constitute the inner peripheral surface of the roller body 16.

That is, the metal plate 60 has a residual curl from the steel plate coil such that the inner peripheral surface of the steel plate coil is concave. That is, the metal plate 60 being formed into the roller body 16 has a residual curl such that it is curved toward the inner peripheral surface of the roller body 16.

Thus, the residual curl does not act, at least, in the direction in which the seam 80 of the roller body 16 opens. Therefore, compared to the case where the metal plate 60 has a residual curl such that it is curved toward the outer peripheral surface of the roller body 16, the seam 80 of the roller body 16 is less likely to open. Thus, even when a stress acts in the direction in which the seam 80 of the roller body 16 opens, the seam 80 can be prevented from being opened. Thus, the transporting roller 31 having high transportation precision can be obtained.

Furthermore, the peripheral direction (bending direction) of the roller body 16 and the winding direction (the rolling direction of the metal plate 60) of the steel plate coil are the same. Thus, the bending direction of the metal plate 60 constituting the roller body 16 and the direction of the curve of the residual curl can be matched. This allows the residual curl of the metal plate 60 constituting the roller body 16 to act in the direction in which the seam 80 of the roller body 16 is closed. Therefore, the seam 80 of the roller body 16 is more effectively prevented from being opened.

Furthermore, it is preferable that shear drop, burrs, and the like, formed on the cutting surfaces of the metal plate 60 be located at the inner periphery of the roller body 16 in the punching process of the roller body 16.

That is, the roller body 16 (transporting roller 31) is formed of the metal plate 60 that is formed by punching, as shown in, for example, FIGS. 19A and 19B. The metal plate 60, serving as the base material of the roller body 16, is bent into a cylindrical shape such that a top surface C2 facing a male mold 131, shown in FIG. 19A, constitutes the outer peripheral surface. Thus, the seam 80 where the end surfaces 61 a and 61 b are in contact with each other is formed.

Thus, even when shear drops sd, sear planes sp, fracture surfaces bs, and burrs (not shown) are formed in the punched metal plate 60 in the punching process, as shown in FIG. 19B, it is preferable that the top surface C2, where the relatively smooth shear drops sd are formed, be located at the outer periphery of the roller body 16. In other words, it is preferable that a bottom surface C1 of the metal plate 60 that is continuous with the burrs and the fracture surfaces bs be located at the inner periphery of the roller body 16.

Thus, the seam 80 can be prevented from being opened due to the irregularity caused by the burrs and the fracture surfaces bs, when the end surfaces 61 a and 61 b of the metal plate 60 are brought into contact with each other to form the roller body 16 having the seam 80.

Therefore, the precision of the seam 80 of the roller body 16 can be increased to provide the transporting roller 15 having high transportation precision. Furthermore, because the burrs are located on the inner peripheral surface of the roller body 16, the burrs are prevented from protruding from the outer peripheral surface of the roller body 16. Thus, a burr removing process can be eliminated, and the production efficiency can be improved.

Furthermore, in addition to the configurations of the unfolded engaging portions shown in FIGS. 13A to 13C, the configurations in which the unfolded engaging portions are formed not at both ends of the metal plate 60 but in the vicinity of the center line in the widthwise direction (bending direction), as shown in FIG. 20A to 20C, are possible. That is, as shown in FIG. 20A, by forming an unfolded engaging portion 76 d formed of a long, narrow, rectangular notch at the end, the engaging portion 73 shown in FIG. 10 can be formed. Furthermore, by forming an unfolded engaging portion 76 e formed of a T-shaped notch shown in FIG. 20B, the engaging portion 74 shown in FIG. 11 can be formed. Furthermore, by forming an unfolded engaging portion 76 f formed of a substantially T-shaped notch shown in FIG. 20C, the engaging portion 75 shown in FIG. 12 can be formed.

Thus, by forming the unfolded engaging portions 76 d to 76 f in the vicinity of the center line in the bending direction, the engaging portions 73 to 75 formed of the unfolded engaging portions 76 d to 76 f can be more precisely formed.

Although the seam 80 of the transporting roller 31 (roller body 16) according to this embodiment extends parallel to the central axis of the roller body 16 formed of a cylindrical hollow pipe, the invention is not limited to such a configuration. For example, the seam formed between the ends of the metal plate 60, serving as the base material, may overlie a straight line on the outer peripheral surface of the cylindrical pipe (roller body), parallel to the central axis of the cylindrical pipe, not over a line segment, but only at one or a plurality of points.

More specifically, as shown in FIG. 21A, a seam 81 may extend over the outer peripheral surface of the roller body 16 in the peripheral direction, from one end to the other end of the roller body 16, not parallel but at an angle to the central axis 16 a of the roller body 16. In order to form such a seam 81, not the above-described long, narrow rectangular metal plate 60, but a metal plate 60 a in the shape of a long, narrow parallelogram, as shown in FIG. 21B, is used as the metal plate serving as the base material, and the metal plate is pressed such that a straight line 16 b is the central axis. Thus, the roller body 16 having the seam 81 at an angle to the central axis 16 a, as shown in FIG. 21A, is obtained.

In the roller body 16 shown in FIG. 21A, the seam 81 extends from one end to the other end of the roller body 16 while making less than one turn around the circumference. This simplifies pressing of the metal plate 60 a. However, as shown in FIG. 21C, a seam 82 may extend from one end to the other end of the roller body 16 while making one or more turns, i.e., spirally, around the circumference. In such a case, the angle θ in the long narrow parallelogram metal plate 60 a shown in FIG. 21B, serving as the base material, is further reduced.

By forming the seam that does not overlie the straight line parallel to the central axis of the cylindrical pipe (roller body 16) over a line segment, but only at one or a plurality of points, the transportation speed of the transporting roller 31 having the roller body 16 is constant when it transports the recording sheet P in cooperation with the driven roller, that is, when it feeds the recording sheet P. Accordingly, uneven transportation is more assuredly prevented.

That is, as shown in FIG. 22, the transporting roller 31 is in contact with the recording sheet P during sheet feeding at, basically, the straight line L on the outer peripheral surface, i.e., the straight line parallel to the central axis 16 a. Therefore, as has been described above, when the seam 80 of the transporting roller 31 (roller body 16) is parallel to the central axis 16 a of the roller body 16, the entirety of the seam 80 of the transporting roller 31 is temporarily (momentarily) in contact with the recording sheet P. If there is a groove due to the seam 80, the groove temporarily comes into contact with the recording sheet P at once, in other words, the overall width of the recording sheet P temporarily comes into contact with the groove due to the seam 80, though the transporting roller 31 according to this embodiment does not suffer such a problem because it has no groove due to the seam 80. As a result, because the groove is recessed from the outer peripheral surface of the transporting roller 31 and has a lower contact resistance to the recording sheet P, the transportation speed temporarily decreases. Thus, uneven transportation occurs.

However, by forming the seam as shown in FIGS. 21A and 21C, even if a groove due to the seam is formed, the groove comes into contact with the recording sheet P during sheet feeding only at one or more points at a time. Therefore, compared to a case where the other surface (line) of the transporting roller 31 comes into contact with the recording sheet P, the contact resistance hardly changes. Thus, the transportation speed becomes constant, and uneven transportation is prevented.

Furthermore, as shown in FIG. 23A, other than the example described above, the seam of the transporting roller (roller body 16) formed of a cylindrical hollow pipe may have rectangular wave-like winding portions 85 formed of straight portions 85 a parallel to the central axis of the roller body 16 and straight portions 85 b that are perpendicular thereto. Even if grooves due to the seam are formed in the seam having the winding portions 85, because the grooves do not come into contact with recording sheet P at once over the overall width of the recording sheet P during sheet feeding, the transportation speed is substantially constant, and uneven transportation is prevented.

Furthermore, the winding portions 85 may be formed over the overall length of the roller body 16, as shown in FIG. 23B, or may be formed selectively at both ends of the roller body 16 except for the middle portion thereof, as shown in FIG. 23C. When the winding portions 85 are formed only at both ends, as shown in FIG. 23C, the intermediate straight portion 86 parallel to the central axis of the roller body 16 extends between the winding portions 85. Although not shown, the intermediate straight portion 86 between the winding portions 85 may extend at an angle to the central axis 16 a, as shown in FIG. 21A.

Furthermore, when the winding portions 85 are formed only at both ends with the intermediate straight portion 86 therebetween, it is preferable that the high-friction layer 50 be formed on the middle portion straight portion 86.

If the winding portions 85 are formed at the seam, or if the winding portions 85 are formed by fitting projections and recesses, it is difficult to fit these winding portions 85 (fitting portions) together in accordance with the design and bring the tips of the projections into contact with the corresponding recesses without leaving a gap therebetween. Thus, if the winding portions 85 are formed over the overall length of the roller body 16, the roller body 16 tends to be strained or twisted. To counter this, by making the winding portions 85 only at both ends, as shown in FIG. 23C, the roller body 16 can be prevented from being strained or twisted. Furthermore, by making the intermediate straight portion 86, not the winding portions 85, serve as the middle portion corresponding to the high-friction layer 50, which directly comes into contact with the recording sheet P, it is possible to assuredly prevent the area which directly comes into contact with the recording sheet P from being strained or twisted.

Furthermore, when the winding portions 85 are formed over the overall length of the roller body 16, as shown in FIG. 23B, a seam 87 including the winding portions 85 may be formed of a plurality of crossing portions 87 a consisting of straight portions 85 b; first straight portions 87 b connecting the ends of the crossing portions 87 a on one side; and second straight portions 87 c connecting the ends of the crossing portions 87 a on the other side, as shown in FIG. 24A. Herein, the first straight portions 87 b and the second straight portions 87 c are formed substantially parallel to the central axis of the roller body 16, and the crossing portions 87 a are formed perpendicular to the first straight portions 87 b and the second straight portions 87 c, that is, perpendicular to the central axis of the roller body 16. Furthermore, the second straight portions 87 c are shorter than the first straight portions 87 b.

When the seam 87 having such a configuration is formed, it is preferable that the distance d3 between the opposed ends at the second straight portions 87 c be larger than the distance d4 between the opposed ends at the first straight portions 87 b. Note that the distance d3 and the distance d4 between the ends are the distances between the ends of the gaps formed on the outer peripheral surface of the roller body 16.

This configuration increases the shape and size accuracy of the roller body 16 in the shape of a cylindrical hollow pipe, and thus, uneven transportation due to deformation or the like of the roller body 16 can be prevented. That is, in the metal plate serving as the base material of the roller body 16, one end constituting the second straight portion 87 c is a protruding piece 87 d whose outline is defined by the adjacent crossing portions 87 a and 87 a and the second straight portion 87 c that connects the ends of the crossing portions 87 a and 87 a. Therefore, when the metal plate is pressed and the protruding piece 87 d is brought toward the opposing end, the tip of the protruding piece 87 d is not sufficiently bent in a cylindrical shape and is higher than the opposing end by the dimension t1, as shown by a two-dot chain line in FIG. 24B, forming a stepped portion at the second straight portion 87 c. Due to the stepped portion, the roller body 16 tends to be deformed, making it difficult to achieve high shape and size accuracy.

By making the distance d3 between the ends at the second straight portion 87 c larger than the distance d4 between the ends at the first straight portion 87 b, which is longer than the second straight portion 87 c, the dimension t2, by which the tip of the protruding piece 87 d is higher than the opposing end, becomes smaller than the dimension t1, as shown by a solid line in FIG. 24B. Thus, the stepped portion is prevented from being formed at the second straight portion 87 c.

Although FIG. 24B shows the dimension t2 in a larger scale for clarity's sake, the dimension t2 is almost zero in actuality, and there is substantially no stepped portion. That is, by preventing the formation of the stepped portion at the second straight portion 87 c, deformation or the like of the roller body 16 due to the stepped portion is suppressed. Thus, the shape and size accuracy can be increased.

Furthermore, when the winding portions 85 are formed only at both ends of the roller body 16, as shown in FIG. 23C, it is preferable that the distance d5 between the opposed ends at the crossing portions 87 a (straight portions 85 b) of the winding portions 85 be smaller than the distance d6 between the opposed ends at the intermediate straight portion 86, as shown in FIG. 25.

In this configuration, the distance d5 is relatively small, and the gap between the ends at the crossing portions 87 a is very narrow. Thus, when the metal plate serving as the base material of the roller body 16 is pressed, the opposed ends constituting the crossing portions 87 a prevents the slip from occurring between one end and the other end in the lengthwise direction (axial direction). Therefore, the roller body 16 (transporting roller 15) is less likely to be strained or twisted, and uneven transportation due to strain or twisting is prevented.

When the winding portions 85 are formed at only both ends of the roller body 16, as shown in FIG. 23C, the distance d7 between the opposed ends at the second straight portion 87 c constituting the protruding piece 87 d of the winding portions 85 may be smaller than the distance d6 between the opposed ends at the intermediate straight portion 86, as shown in FIG. 25, or may be larger than the distance d6.

By making the distance d7 smaller than the distance d6, the gap between the opposed ends can be more easily made constant over the overall length of the seam, and the shape and size accuracy of the roller body 16 is further increased. That is, because the length of the intermediate straight portion 86 is larger than the length of the second straight portion 87 c at the winding portions 85, the ends at the intermediate straight portion 86 can be more precisely brought toward each other than the ends at the second straight portion 87 c. Thus, even if the distance between the ends at the intermediate straight portion 86, where the precision of the gap between the ends is relatively high, is increased to increase the gap compared to the distance between the ends at the second straight portion 87 c, the gap can be made sufficiently constant. Accordingly, uneven transportation due to strain or twisting of the roller body 16 can be prevented.

On the other hand, if the distance d7 is larger than the distance d6, as shown in FIG. 24B, the dimension t2, by which the tip of the protruding piece 87 d is higher than the opposing end, decreases. Thus, the stepped portion is prevented from being formed at the second straight portion 87 c. Because the formation of the stepped portion at the second straight portion 87 c can be prevented, deformation of the roller body 16 due to the stepped portion can be suppressed. Thus, the shape and size accuracy can be increased and uneven transportation is prevented.

Furthermore, in the above-described embodiment, the transporting roller of the invention is applied to the transporting roller 31 of the transporting roller mechanism 19. However, transporting roller of the invention may be applied to the sheet-discharging roller 41, the sheet-discharge serrated roller 42, or the driven rollers 32 (roller 32 a) of the transporting roller mechanism 19. 

1. A printing apparatus comprising a transporting roller formed of a metal plate bent into a cylindrical shape, wherein the transporting roller has a first driving member that transmits a rotational driving force to the transporting roller, and a second driving member that transmits the rotational driving force transmitted thereto to a processing unit that performs printing-related processing, the first and second driving members being provided on one end side of a transporting area where recording media are transported.
 2. The printing apparatus according to claim 1, wherein the processing unit operates while the recording media are transported.
 3. The printing apparatus according to claim 1, wherein a seam of the metal plate constituting the transporting roller includes an intermediate straight portion that is located in the transporting area and is formed linearly in the axial direction, and a crossing portion that is located on one end side of the transporting area and is formed by fitting a recess and a projection provided at the end surfaces of the metal plate around the axis so as to extend in a direction intersecting the axial direction.
 4. The printing apparatus according to claim 1, wherein a third driving member is provided on the other end side of the transporting area of the transporting roller, the third driving member transmitting a rotational driving force transmitted thereto to a second processing unit for performing printing-related processing, which does not operate while the recording media are transported.
 5. The printing apparatus according to claim 4, wherein the seam of the metal plate constituting the transporting roller includes an intermediate straight portion that is located in the transporting area and is formed linearly in the axial direction, and a second crossing portion that is located on the other end side of the transporting area and is formed by fitting a recess and a projection provided at the end surfaces of the metal plate around the axis so as to extend in a direction intersecting the axial direction. 